[POWERPC] Update xmon slb code

This adds a bit more detail to the xmon SLB output.  When the valid
bit is set, this displays the ESID and VSID values, as well as
decoding the segment size -- 1T or 256M -- and displaying the LLP
bits.  This supresses the output for any slb entries that contain only
zeros.

sample output from power6 (1T segment support):
00 c000000008000000 40004f7ca3000500  1T  ESID=   c00000  VSID=       4f7ca3 LLP:100
01 d000000008000000 4000eb71b0000400  1T  ESID=   d00000  VSID=       eb71b0 LLP:  0
08 0000000018000000 0000c8499f8ccc80 256M ESID=        1  VSID=    c8499f8cc LLP:  0
09 00000000f8000000 0000d2c1a8e46c80 256M ESID=        f  VSID=    d2c1a8e46 LLP:  0
10 0000000048000000 0000ca87eab1dc80 256M ESID=        4  VSID=    ca87eab1d LLP:  0
43 cf00000008000000 400011b260000500  1T  ESID=   cf0000  VSID=       11b260 LLP:100

sample output from power5 (notice the non-valid but non-zero entries)
10 0000000008000000 00004fd0e077ac80 256M ESID=        0  VSID=    4fd0e077a LLP:  0...